window.addEvent('domready', function() {

 var select_kraj = $('select-kraj');

 var select_okres = $('select-okres');

 var Req = new Request.HTML();

 select_kraj.addEvent('click', function(event){

  event.stop();

  var selected = this.value;

  Req.setOptions({

    url:AplRoot+'ajax.php',

    method: 'get', 

    data: 'action=okresy&kr_id=' + selected,

    onSuccess: function(objects, object_list, html) {

      select_okres.set('html', html);

      alert('x');

      this.empty();

    },

   })

   Req.send();

  })

});